Question:

Assuming the balls to be identical except for difference in colours, the number of ways in which one or more balls can be selected from 10 white, 9 green and 7 black balls is:

879

880

629

630

Number of ways of selecting one or more balls from 10 white, 9 green and 7 black balls=(10+1)(9+1)(7+1) = 11 × 10 × 8 = 880